Security element

ABSTRACT

A bar code is integrated in the paper in the form of a watermark. The fields ( 6 ) which separate the information-conveying bars of the bar code from each other are formed as watermarks. The information-conveying bars can be formed as watermarks, but they do not have to. Their width results from the spacing of the separating fields ( 6 ). The separating fields ( 6 ) are more narrow than the information-conveying bars, as a result of which the total length of the bar code is kept short.

This application is a National Phase of PCT Application Serial No.PCT/EP03/03059, filed Mar. 24, 2003.

FIELD OF THE INVENTION

The invention relates to a security element, namely a bar code in theform of a watermark, as well as a security paper and a document of valueor security document manufactured thereof, such as for example banknote, check, share, identity card, ticket for public transport,admission ticket and the like, with such a bar code, and furthermore amethod and a papermaking screen for manufacturing the security paper.

BACKGROUND OF THE INVENTION

It is known to incorporate a bar code in a paper in the fashion of awatermark, in particular in a security paper, for manufacturing securitydocuments or documents of value. For example, the authenticity of banknotes can be tested with reference to the bar code, if all bank notes ofa certain value and a certain date of issue bear a certain watermark inthe same fashion. By comparing with the serial number and thedenomination printed on the bank note then the authenticity of the banknote can be checked with reference to the bar code. Depending on thecomplexity of the information encoded in the watermark bar code, the barcode can become comparatively long, which is undesirable with smalldimensioned documents of value, such as for example bank notes.

The problem, however, is not only the length of the bar code, but inparticular its checkability for the purpose of determining theauthenticity. Because the broader the bars incorporated as a watermarkin the paper, the more irregular is their appearance on transmissiveviewing. The reason for this is that a watermark with a regular darksurface can be realized only with difficulties. For manufacturing thewatermark the papermaking screen is embossed, so that the deposit ofpaper fiber during the sheet formation is influenced. If the papermakingscreen is deep-embossed, more paper pulp deposits in this area, while ahigh-embossing impedes the deposit of paper pulp. With an embossedsurface above all the edges of the surface are reproduced well. Thesurface itself towards its inner area becomes either lighter or darker.

SUMMARY OF THE INVENTION

It is the problem of the present invention to propose a bar code in theform of a watermark, which is more versatile and comparativelyspace-saving. A further problem of the invention is to provide asecurity paper equipped with such a bar code and papers of value orsecurity documents manufactured thereof, as well as a method and apapermaking screen for manufacturing the security paper.

These problems are solved by a bar code, a security paper, a securitydocument, a method and a papermaking screen according to the presentinvention.

Accordingly, the separating fields, through which theinformation-conveying bars are separated from each other, are formed asuniquely detectable watermarks. These separating fields are detected as(separating-field) bars by the bar-code reader. The actual bar codeinformation, however, is not determined by the width of the detected(separating-field) bars but by the width of the fields located inbetween the detected (separating-field) bars, these fields representingthe actual bars of the bar code. I.e., beginning and end of theinformation-conveying bars are each marked by the separating-field bars.

This offers the two following substantial advantages compared to priorart. Firstly, the information-conveying bars of the bar code locatedbetween the separating fields can be selected in any width. Since thelightness of the information-conveying bars is not taken into accountwhen evaluating, there exist no problems with an irregularly filled barsurface appearing dark or light in transmitted light. Secondly, theseparating fields can be formed extra narrow, in particular by usingelectrotypes on the papermaking screen, as a result of which the totallength of the bar code is comparatively short and space-saving.

As to further reduce the length of the bar code, it is advantageous toform the bar code as a two-dimensional bar code, which has several e.g.parallel information tracks.

A particularly advantageous embodiment of the invention provides thatthe fields located between the separating fields, which form theactually information-conveying bars of the bar code, are not designed asa watermark, so that in transmitted light only the separating fields canbe recognized as watermark bars. The first and the last separating fielddefine the boundaries of the bar code.

As to increase the contrast, the information-conveying bars of the barcode, too, can have the design of a watermark, the separating fieldsbeing formed as light watermarks and the information-conveying bars asdark watermarks—or vice versa It is preferred that not theinformation-conveying bars are formed as light watermarks but theseparating fields, since otherwise with light information-conveying barsat increasing width of the bars there would exist a danger of formationof holes in the paper.

According to a special embodiment of the invention a separating fieldlocated at the edge of the bar code, which means a first or lastseparating filed, for example by means of its characteristic width orits fiber density defines the information content to be assigned to thebars of different width, i.e. whether a broad bar indicates a “1” and anarrow bar a “0” or vice versa. Alternatively, the first bar can bedefined as a startbit and its width can indicate, whether a broad bar ofthe bar code indicates “1” and a narrow bar “0” or vice versa.

According to a preferred embodiment, an inventive security document ordocument of value is equipped with an additional storage medium. Thiscan be for example a magnetic storage medium, such as a magnetic track,or an electronic storage medium, such as a microchip with integratedcircuits. With such an embodiment the bar code can contain data forencoding and decoding of information instead of the value of thedocument. In the storage medium can be stored in an advantageous fashionthe document value rendered by the bar code together with the serialnumber of the document, or for example the result of a predeterminedcombining of the value factor and serial number. With that theforgery-proofness and the checkability of the authenticity of a documentis increased. The storage of the combining in the additional storagemedium can be effected when manufacturing the document or at the time ofbringing it into circulation. When testing the authenticity the resultof the combining can be read from the storage medium. If the way ofcombining is known, together with the document value which very easilycan be read out from the bar code watermark, the serial number can bereconstructed. If in addition the serial number is read directly fromthe document, a further possibility arises for checking whether aread-out storage medium really belongs to an individual document such asfor example a bank note.

Furthermore, coincidences in the formation of the inventive bar code,such as the cloudiness of the paper in the bar code area orirregularities in the run of the edge of individual sections, can beused as an additional measured value, so as to increase theforgery-proofness of a document or to improve the authenticity testing.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following the invention is described by way of example withreference to the accompanying figures.

FIG. 1 shows a bank note with an inventive watermark bar code,

FIG. 2 shows a transmitted light view of an inventive watermark barcode,

FIG. 3 shows a transmitted light view of a further inventive watermarkbar code,

FIG. 4 schematically shows a papermaking screen in cross section,

FIG. 5 shows a transmitted light intensity curve according to a firstembodiment of an inventive watermark bar code,

FIG. 6 shows a transmitted light intensity curve according to a secondembodiment of an inventive watermark bar code,

FIG. 7 shows a transmitted light intensity curve according to a thirdembodiment of an inventive watermark bar code,

FIG. 8 shows a transmitted light view of a watermark bar code accordingto prior art,

FIG. 9 shows a transmitted light intensity curve of a watermark bar codeaccording to prior art, and

FIG. 10 shows a transmitted light intensity curve of a watermark barcode according to a further prior art.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows in an exemplary fashion as one of many possible documentsof value and security documents a bank note 1 with the denomination 2 of“EUR 100”. The bank note 1 has a two-dimensional bar code 3, which isintegrated in the fashion of a watermark in the security paper, out ofwhich the bank note 1 is manufactured.

Documents of value with a one-dimensional bar code in the form of awatermark are already known from prior art. The broader the barsincorporated in the paper as a watermark, the more irregular theirappearance in transmitted light, so that the evaluation of the bars isvery problematic. This is shown in FIG. 8, which schematically shows awatermark bar code 3 viewed in transmitted light. The bar code 3 wasproduced with an embossed papermaking screen, which in its embossedareas producing the bars 5 of the bar code 3 promotes the deposit ofpaper fiber. However, the fiber density i.e. the paper thickness,decreases towards the inner areas of the surface of the bar, so that theedge area of the surface can be imaged well, but the inner areas of thesurface in transmitted light appear lighter vis-a-vis the edge areas.This is graphically shown in FIG. 9, where the transmitted lightintensity I⁺, I⁻ deviating from a normal transmitted light intensity I₀is plotted. It can be recognized that the transmitted light intensity Iin the center of the bars comes the closer to the normal transmittedlight intensity I₀, the broader the bar is. Here it has to be taken intoaccount that the normal transmitted light intensity value I₀ in FIG. 9is shown in an idealized way. Actually, this value I₀, varies about anaverage value, so that with broad bars it can occur that a bar codesensor signalizes the end of a bar 5 or the beginning of a separatingfield 6, although not more than the middle of the bar 5 has beenreached. This can lead to read errors, because a broad bar 5 may beinterpreted as two short bars by mistake.

The alternative, to use a light bar code instead of a dark bar code, hasthe same disadvantage, namely that the fiber density decreases towardsthe middle of the bar. Again the result is not a regularly light bar ofthe desired dimension. Furthermore, with broad bars there exists thedanger of formation of holes in the paper.

In FIG. 10 is shown the transmitted light intensity I of a bar codeknown from DE 30 34 916 A1, where the problems described above do notarise. According to this the areas of the papermaking screen used forproducing the bars of the bar code are embossed as rectangular, notisosceles triangles in the papermaking screen. The part of thewatermark, which is produced by means of the steep edge in the paper, intransmitted light is easily recognizable as distinctive dark or lightstripe and marks the beginning of a bar 5. Whether the bar 5 represents“1” or “0”, does not depend on its width but on the fact, whether thebar is light or dark, which means whether the embossing of thepapermaking screen starting from the level of the papermaking screen isdirected downwards or upwards. As a result of this also the length ofthe whole bar code can be kept short, because separating fields 6between the individual bars 5 for the clear delimitation from each othercan be omitted. Disadvantageous, however, is the fact, that the bar codeis restricted to a digital encoding, because only light and dark fieldsare differentiated.

The FIGS. 2 and 3 each show a part of the different embodiments of awatermark bar code 3 from FIG. 1 according to line AA upon viewing intransmitted light. In both cases and also in the examples explained inthe following, the bar code is a digital bar code consisting of zerosand ones, the width of the bar indicating the value “0” or “1”. The bars5 are separated from each other by separating fields 6, the first andthe last separating field defining the boundaries of the bar code. Thebar codes shown in FIGS. 2 and 3 thus each read 0-1-1-0.

With the embodiment according to FIG. 2 the separating fields 6 appeardark compared to the bars 5. That means, in the areas of the separatingfields 6 the bank note has an increased fiber density, which has beenproduced by a respective embossing of the papermaking screen used formanufacturing of bank note paper. This embossing of the papermakingscreen causes an increased deposit of paper fiber during thepapermaking, by means of which the transmitted light intensity, when thepaper is viewed in transmitted light, is decreased respectively and theseparating fields 6 appear dark. The bars 5, which define the actualinformation of the bar code, in transmitted light appear neither lighternor darker than the bank note material surrounding the bar code, sincethe bars 5 do not have any watermark characteristics. Since due to thisfact not the information-conveying bars 5 but the separating fields 6are detected by means of a bar code reader, the width of theinformation-conveying bars is determined merely indirectly via thedistance between the detected separating fields 6.

The same applies to the embodiment shown in FIG. 3, in which, deviatingfrom the embodiment according to FIG. 2, the separating fields 6 of thebar code appear light, except for the separating field on the extremeleft. The light separating fields 6 can be produced particularlystrikingly by using so-called electrotypes. Electrotypes, in general,are small metal parts, which are fixed on one side of the papermakingscreen, for example soldered or by means of brackets which are put intothe mesh of the screen and bent over. With that very narrow andparticularly light transmitted light effects can be obtained, which areeasily to detect by sensors.

The extreme left separating field 6 in FIG. 3 defines that the followingbroad bars are to be counted as “0” and the narrow bars 5 as “1”, as itis the case in FIG. 2. If the extreme left separating field 6 would beformed as a light separating field, like all other separating fields 6,then the information content of the bars 5 would be the other way roundand the whole information of the bar code would not read 0-1-1-0 but1-0-0-1.

Instead of the characteristic transmitted light intensity or fiberdensity of the extreme left separating field 6—it could also be theextreme right separating field 6—also the width of the separating fieldcould be related to, so as to indicate the information content of thebroad and narrow bars 5. The two possibilities can also be combined, inparticular as to define further information of the bar code.

Alternatively or additionally, also the first or the last bar 5 canserve as a startbit or endbit, for example, the width of the startbitbar or endbit bar giving information on whether the broad bars arecounted as “0” and the narrow bars as “1” or vice versa.

In FIG. 4 by way of example and only schematically is shown a part of apapermaking screen 8, with which a paper with a watermark bar codeaccording to FIG. 3 can be manufactured. For that the papermaking screen8 has electrotypes 7 appropriately spaced-apart on its papermakingsurface for producing the light separating fields 6, as well as adeep-embossed area 9 for producing the extreme left separating field 6that has an increased paper thickness or fiber density and thereforeappears dark in transmitted light.

FIG. 5 shows an idealized course of the transmitted light intensity of abar code similar to that shown in FIG. 2 with dark separating fields 6and with information-conveying bars 5. The transmitted light intensity Iin the areas of the separating fields 6 lies below a normal transmittedlight intensity I₀ of bank note paper, since the fiber density F in theareas of the separating fields 6 is respectively high. The transmittedlight intensity curve I thus coincides with the fiber density curve F,if the intensity increase I⁺ is plotted upwards and the fiber densityincrease F⁺ downwards. Transmitted light intensity curve and fiberdensity curve therefore are both described with reference number 4.

FIG. 6 shows the curves of the transmitted light intensity and the fiberdensity 4 for a bar code similar to that shown in FIG. 3. In this casethe transmitted light intensities I in the areas of the separatingfields 6 lie above the normal transmitted light intensity I₀, except forthe extreme left separating field 6, the transmitted light intensity Iof which lies below the normal transmitted light intensity I₀. Incontrast to the description according to FIG. 5 the transmitted lightintensity curve in FIG. 6 is shown in a less idealized fashion, as aresult of which it becomes apparent, that the transmitted lightintensity or fiber density, despite of its in general regulardistribution I₀, F₀ along the extend of the bar 5 of the bar code,slightly varies about an average value I₀ or F₀, which indicates the“normal transmitted light intensity” and “general fiber density”.

In FIG. 7 a further embodiment of the invention is shown. Basically itis a combination of the prior art according to FIG. 9 and the embodimentaccording to FIG. 6 or FIG. 3. That means, the separating fields 6 aswell as the bars 5 are integrated in the paper in the fashion of awatermark, the information-conveying bars 5 in transmitted lightappearing as dark areas with somewhat lighter centers, at the outsetdescribed as disadvantageous, and the separating fields 6 appearing asstrikingly light lines easily to identify. The particularly hightransmitted light intensity in the areas of the separating fields 6exceeds the transmitted light intensity in the lighter center areas ofthe information-conveying bars 5 in such a way, that amisinterpretation, as explained at the outset, can be ruled out. Theembodiment according to FIG. 7 compared to the embodiments according tothe FIGS. 5 and 6 or 2 and 3 offers an additional increase of contrastbetween the areas of the bars 5 and the separating fields 6 and thus animproved readability of the bar code.

1. Security paper with a general fiber density (F_(o)) for manufacturinga document of value or security document, comprising a bar codeincluding information-conveying bars separated from each other byseparating fields, characterized in that the separating fields areincorporated as a watermark in the security paper, so that a fiberdensity of the security paper in an area of these separating fieldsdeviates from a general fiber density of the security paper.
 2. Securitypaper according to claim 1, wherein the fiber density of the securitypaper in the areas of the information-conveying bars deviates in adifferent positive or negative direction from the general fiber densityas compared to the areas of the separating fields.
 3. Security paperaccording to claim 2, wherein the fiber density of the security paper inthe areas of the information-conveying bars is higher and in the areasof the separating fields slower than the general fiber density. 4.Security paper according to claim 1, wherein the fiber density of thesecurity paper in the areas of the information-conveying barscorresponds to the general fiber density.
 5. Security paper according toclaim 1, wherein the separating fields are more narrow than theinformation-conveying bars.
 6. Security paper according to claim 1,wherein the security paper when viewed in transmitted light at least inone of the separating fields appears lighter than in an area of thesecurity paper with the general fiber density, and at least in one ofthe other separating fields appears darker than in an area of thesecurity paper with the general fiber density.
 7. Security paperaccording to claim 1, wherein an information-conveying bar located at aboundary of the bar code has a characteristic property as to indicate,which information content is assigned to each of the various bars ofdifferent width of the bar code.
 8. Security paper according to claim 7,wherein the characteristic property is at least one of width and fiberdensity of the bar located at the boundary.
 9. Security paper accordingto claim 1, wherein the bar code is a two-dimensional bar code. 10.Security document or document of value comprising a security paperaccording to claim
 1. 11. Security document or document of valueaccording to claim 10, selected from the group of documents: bank note,check, share, identity card, ticket for public transport, admissionticket.
 12. Method for manufacturing a security paper with a generalfiber density for a security document or document of value, with a barcode including information-conveying bars separated from each other byseparating fields, wherein the security paper in areas of the separatingfields is produced as a watermark with a fiber density deviating from ageneral fiber density of the security paper.
 13. Method according toclaim 12 using a papermaking screen, which is formed in a special way inthe areas of the separating fields, so that in this areas the deposit offibers for producing a watermark is influenced positively or negativelyin the security paper to be manufactured.
 14. Method according to claim13, wherein the papermaking screen in the areas of theinformation-conveying bars is formed in such a way that in these areasthe deposit of fibers is influenced neither positively nor negatively.15. Method according to claim 13, wherein the papermaking screen in theareas of the information-conveying bars is embossed in such a way thatthe deposit of fibers in these areas is influenced positively. 16.Method according to claim 12, wherein the papermaking screen at least inthe area of one of the separating fields is embossed in such a way thatthe deposit of fibers is influenced positively.
 17. Method according toclaim 1, wherein the papermaking screen at least in the area of one ofthe separating fields is equipped with an electrotype, so that thedeposit of fibers is influenced negatively.
 18. Papermaking screen formanufacturing a security paper with a bar code which includesinformation-conveying bars separated from each other by separatingfields, wherein the papermaking screen has areas for producing theseparating fields, in which the papermaking screen is especially formedso as to positively or negatively influence the deposit of fibers inthese areas for producing a watermark in a paper to be manufactured withthe papermaking screen.
 19. Papermaking screen according to claim 18,wherein the papermaking screen in its areas producing theinformation-conveying bars is formed in such a way, that in these areasthe deposit of fibers is not especially influenced and a watermark isnot produced in a paper to be manufactured with the papermaking screen.20. Papermaking screen according to claim 18, wherein the papermakingscreen in its areas producing the information-conveying bars isembossed, so as to positively influence the deposit of fibers in theseareas for producing a watermark in a paper to be manufactured with thepapermaking screen.
 21. Papermaking screen according to claim 18,wherein the papermaking screen is embossed in at least one of its areasproducing the separating fields, so as to positively influence thedeposit of fibers for producing a watermark in a paper to bemanufactured with the papermaking screen.
 22. Papermaking screenaccording to claim 18, wherein the papermaking screen at least in one ofits areas producing the separating fields is equipped with anelectrotype, so as to negatively influence the deposit of fibers forproducing a watermark in a paper to be manufactured with the papermakingscreen.
 23. Papermaking screen according to claim 18, wherein the areasof the papermaking screen for producing the separating fields are formedmore narrow than those areas of the papermaking screen for producing theinformation-conveying bars.
 24. Security paper according to claim 1,characterized in that it has an additional storage medium.
 25. Securitydocument or document of value according to claim 10, characterized inthat the document has an additional storage medium.
 26. The securitypaper of claim 1 wherein said document of value or security document isa bank note, check, share, identity card, ticket for public transport oradmission ticket.
 27. The method of claim 12 wherein said securitydocument or document value is a bank note, check, share, identity card,ticket for public transport or admission ticket.
 28. The security paperof claim 24 wherein said additional storage medium is an area formagnetic storage of information or a microchip.
 29. The securitydocument or document of value of claim 25 wherein said additionalstorage medium is an area for magnetic storage of information or amicrochip.